Selenium protects against some cancers
Selenium reduced the incidence of colon, rectal, prostate, and lung cancer in a ten-year study of 1,312 people at the University of Arizona Cancer Center in Tucson. Participants in the randomized, double-blind study who took 200 micrograms of selenium supplements daily had a lower incidence of these cancers and 17 percent fewer cancer deaths than those who did not take it. No adverse effects were reported, but further studies are needed before daily selenium supplements can be recommended, researchers said.
Selenium is a trace mineral required by the body and a potent antioxidant which can be found in liver, meat, seafood, grains, and vegetables. (4)
Antioxidants: Heralds of hope in the war on cancer
The second most common cause of death in the United States, some form of cancer will affect nearly one out of every four Americans during their lifetime.
In the search for effective weaponry in the battle against cancer, antioxidants offer hope as a preventive measure and treatment. Some antioxidants are formed in the body, but two primary dietary sources of antioxidants are fruits and vegetables.
People who eat a well-balanced, diverse diet including at least five servings of fruits and vegetables a day have been shown to have a lower risk of cancer. In Linxian, China, which has one of the world’s highest rates of esophagus and stomach cancers, 29,584 people aged forty to sixty-nine were given daily vitamin and mineral supplements and studied over a five-year period. Those participants who received one to two times the U.S. RDA of vitamin E, beta-carotene, and selenium—antioxidants commonly found in many fruits and vegetables—had significantly fewer cancer deaths. Other clinical trials have shown that vitamins decrease the risk of gastric, esophageal, colon, cervical, and breast cancers.
Free-radical chain reactions
All cancers are characterized by cells growing out of control. An impaired immune system, the absence of particular enzymes, and DNA damage all can cause this abnormal cell growth, “but the mechanism of cell damage is the same in all cancers,” said Richard Passwater, director of research for the Solgar Nutritional Research Center. The cell damage is caused by free radicals, atoms or molecules with one or more unpaired electrons. Being unstable, they steal an electron from another molecule to regain balance, in the process creating another free radical. Air pollution, heavy exercise, stress, exposure to carcinogenic chemicals including cigarette and cigar smoke, and fatty foods all promote the formation of free radicals.
The antioxidant defense
Each antioxidant has its own profile of actions against the various free radicals, Passwater said. Antioxidants can be classified into several key groups that use a tag-team approach to protect the body. Alexander Schauss, at the Southwest College of Naturopathic Medicine and Health Sciences in Tempe, Arizona, and the American Institute of Biosocial Research in Tacoma, Washington, described the actions of these different types of antioxidants:
• Vitamins. Fat-soluble vitamins such as vitamins E and A and the vitamin A precursor beta-carotene protect lipids in cell membranes by neutralizing free radicals. Water-soluble vitamin C attacks free radicals in blood and regenerates vitamin E. At least two studies have found that vitamins E and C combined with selenium work better together to lower cancer risk than when taken separately.
• Enzymes. Superoxide dismutase, which turns the free radical superoxide ion into the less harmful free radical hydrogen peroxide, and glutathione peroxidase are two antioxidant enzymes that stimulate the immune system and help DNA molecules repair themselves. Another enzyme, catalase, then converts hydrogen peroxide into harmless water. Glutathione, a peptide, is the body’s major antioxidant, and eating foods containing sulfur assists in its manufacture. Glutathione, vitamin E, and amino acids protect the liver from free-radical damage.
• Minerals. Zinc, copper, iron, magnesium, manganese, and selenium are essential for the manufacture of antioxidant enzymes in the body. Zinc, copper, and manganese are components of superoxide dismutase. Selenium is a component of glutathione peroxidase and works with vitamin E to neutralize free radicals. Iron is a component of catalase. Until optimal dosages are determined, do not exceed the RDA of any of these minerals as an excess of one can block the absorption of another.
• Coenzyme Q10 (CoQ10). CoQ10 works with other enzymes to utilize vitamins and minerals. Studies show that CoQ10 plays a vital role in the health of the immune system, eases some side effects of chemotherapy, and has reduced mortality from tumors and leukemia in animals. As we age, the amount of CoQ10 produced by the body decreases.
• Phytochemicals. These include polyphenols such as catechin, which is found in green tea; anthocyanidins in grape seeds; ellagic acid in grapes, nuts, and berries; phenolic acids in red wine and soybeans; isoflavones in soybeans; thiols in onion and garlic; carotenoids in red, orange, and yellow fruits and vegetables; limonoids in citrus fruit peels; indoles in broccoli, cabbage, and brussels sprouts; and bioflavonoids in citrus fruits.
• Uric acid. Produced in the body, it neutralizes free radicals in the cellular fluid. The mineral molybdenum is required for its production.
Antioxidants at work
Although most medical studies have been performed on a single antioxidant, some alternative practitioners maintain that a combination of antioxidants offers more complete cell protection. Antioxidants interact with free radicals at different speeds, stages of activity, and sites in the body, according to Michael Cronin, a naturopathic physician and president of Southwest College of Naturopathic Medicine and Health Sciences. Some smaller antioxidant molecules can penetrate the cell to protect the mitochondrial membrane (the cell’s source of energy, where proteins are synthesized and lipids metabolized). Larger ones bind to proteins on the cell surface. Vitamin E, for example, is a large molecule that works in lipid membranes and vessels to repair damage. Because it is fat-soluble, Cronin recommends that it be taken with the meal containing the most fat. Vitamin C, on the other hand, is water-soluble, moves freely in the blood, acts rapidly, and does not remain in the body long. Cronin recommends taking it in small doses several times a day.
Passwater recommends that people take an antioxidant formula because he feels that many multivitamin/multimineral supplements do not contain adequate amounts of antioxidants. Alexander Schauss advises buying those derived from natural sources over synthetic versions because the two act differently at the cellular level. For example, natural vitamin E is 36 percent more biologically active and is retained in tissues longer than synthetic vitamin E produced from petroleum.
During cancer treatment
Medical trials have shown antioxidants to be effective at diminishing the side effects of radiation and chemotherapy, enhancing the effectiveness of certain chemotherapeutic drugs and other conventional cancer therapies, and transforming cancer cells into normal cells, according to Kedar Prasad, physician and author of Vitamins in Cancer Prevention and Treatment. Antioxidants can also support the immune system in fighting the spread of cancer to other parts of the body, Cronin maintains. Although chemotherapy kills cancer cells, it also creates free radicals that can in turn cause more cell damage.
Antioxidants are relatively inexpensive, easy to use, and incorporate into a diet, and studies point to their usefulness and effectiveness in preventing and treating cancer. More research is needed to explore their potential in these roles, however.
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Lien, E. J., and W. Y. Li. Anticancer Chinese Drugs and Related Plants. New Canaan, Connecticut: Keats, 1996.
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Passwater, Richard A. Cancer Prevention and Nutritional Therapies. New Canaan, Connecticut: Keats, 1993.
Prasad, Kedar. Vitamins in Cancer Prevention and Treatment. Rochester, Vermont: Healing Arts Press, 1989.